The present invention relates to a programmable movement, multiple position machine, and in particular to such a machine which by its electronically programmable control accomplishes multiple position movement in a pre-defined, carefully controlled but easily adjustable fashion. The apparatus of the present invention can be used, for instance, as an assembly machine or a material moving or handling machine for the transferring of work between stations, machine operations, or automatic work handling devices.
Prior art work transfer and positioning devices in the assembly machine field have included multiple position indexers and indexing machine chassis. Indexers and indexing machine chassis have widespread commercial application to relatively high speed multiple position production machines. Such machines are typically "dedicated" to one task or set of tasks, and are used for such operations as multiple position machining, testing, heating, cooling, and assembly. One of the more common lines of indexers and indexing machine chassis utilize a cam to translate continuous motor input to intermittent output motion which in turn moves and stops a series of work handling fixtures or work positions themselves. The number of output positions of such a drive are typically not variable, but are fixed by the relationship of the cam to its driven components.
One particular type of multiple position production machine is a rotary assembly machine, such as disclosed in U.S. Pat. Nos. 2,921,478, 3,065,530 and 3,231,968, assigned to the assignee of the present invention, and includes an indexer for a rotary table which is moved or indexed in a number of selected increments. As the table is indexed in the various increments, assembly or test processes are performed on parts resting on the table. The assembly machine can also be of the in-line variety, having a continuous or articulated belt or articulated links on which the part to be worked on is also intermittently indexed through a number of work stations.
An indexer associated with such a rotary assembly machine is the apparatus that moves the rotary table incrementally. Such an indexer is typically actuated mechanically by a motor driven cam. The cam is so shaped that it engages and imparts motion to a series of followers in order to rotate the table during a particular portion of the rotation of the cam, and then disengages from the followers, or the cam is shaped so that it no longer imparts displacement motion to such followers, so that the table dwells or remains at a fixed position during another period of rotation of the cam. The dwell period may be a major portion of the cam rotation cycle period.
In order to accomplish the required precise movements, the cam that controls the indexer must be cut carefully and to an exactly prescribed design. In these mechanically controlled indexers of the prior art, such as disclosed in U.S. Pat. Nos. 2,887,209, 2,921,478, 2,990,940, and 3,039,597, assigned to the assignee of the present invention, a new cam must be used for each type of indexing motion desired. Typical indexers of the prior art do not require variable acceleration, direction of motion, and length of travel indexing, so a mechanical cam control of indexing is satisfactory. The utility of such indexers is, however, limited because of the difficulty of mechanically changing the cam design so as to provide adjustable incremental motion for various operations. Therefore, cam driven indexers associated with such prior art machines have limited utility for variable work transfer applications.
Within recent years, automatic parts handling machines have been developed that are commonly called "robots." Such robots can perform a number of movements with respect to a work piece; they may also move the work piece to its work place and remove it from the work place. The mechanical hands of such robots may grasp, rotate, and operate a work piece. The proliferation of such robot technics has required the use of more versatile and sophisticated work transfer machines to bring the work to and take the work from the robot location, and have heightened the need for an apparatus such as the present invention, i.e., one that accomplishes multiple position movement in a pre-defined, carefully controlled but easily adjustable fashion.